1. Technical Field
The present invention relates to cognitive radio systems and methods and, more particularly, to spectrum sensing for cognitive radio.
2. Description of the Related Art
In cognitive radio (CR) networks, secondary users (SUs) are permitted to opportunistically access a licensed spectrum band or channel at times that the band or channel is not occupied by primary users (PUs). An important aspect of CR networks is the maintenance of the quality of service (QoS) of secondary transmissions while ensuring that that the secondary transmissions do not interfere with primary user (PU) transmissions on the licensed band. To avoid causing harmful interference to PUs, SUs should reliably detect the return of PUs and quickly evacuate from the spectrum band occupied by the SUs. However, to maintain QoS of secondary traffic, SUs should quickly switch to another empty spectrum band that is not utilized by any PUs.